If Magnus keeps winning and his opponents stay around the elo they are at, wouldn't Carlsen then get fewer points per win? Making this quest take even longer
Carlsen and the quest for 2900

Yeah, Carlsen will get fewer and fewer points for winning, and lose more for drawing and losing, which is what makes rising to such a high ELO very difficult.
Kasparov's feat of reaching 2851 was against players with much lower ELOs than Carlsen is facing, though arguably, they were equally difficult to play against.
Fischer's 2785 in 1972 was far and away the most impressive ELO rating, IMHO, given there was no one else above 2700 at the time.

Carlsen's rating 2 years ago was 2835. Since then he has played 103 games, and his rating has improved 46 points. This is actually a great achievement, given how hard it is to gain ratings points when your opponents are on average 100 points below you.
He can't and won't break 3000 while there are only 1 or 2 others above 2800.
This is correct. Lower rated opponents makes it extremely difficult to advance very far.
Here is how Carlsen's ratings will change based on the strength of his opponents. Let's give him 100 games (about how many games he's likely to play in two years. Let's also assume he averages 70% over this period.
Avg. Opp: 2750, Score 70/100, Rating = 2895
Avg. Opp: 2775, Score 70/100, Rating = 2913
Avg. Opp: 2800, Score 70/100, Rating = 2932
If he were to reach 3000, it is likely to take longer than the time it took him to rise from 2760 - 2880 (6 years).
I think Carlsen's main focus is on winning tournaments, and letting the rating take care of itself. It's a nice by-product, but not the main goal. That being said, I for one would find it a fantastic achievement.

after he beats Anand 10 straight times, he should reach 3000 quite easily
If he beat Anand 10 times in a row his rating would be 2918:
http://www.kosteniuk.com/EloCalc/elo.php

after he beats Anand 10 straight times, he should reach 3000 quite easily
If he beat Anand 10 times in a row his rating would be 2918:
actually if he beats Anand 9 times, he would reach 3003 according to http://www.kosteniuk.com/EloCalc/elo.php

feels good to see the greatest chess player of all time finally reach the 2900 barrier, Carlsen is truly a once in a lifetime player.
This makes me think of something most people never seem to. My father was alive to see Fischer dominate in the early 70's. He then saw Kasparov surpass Fischer's record. He's still alive and well, so he's seen Carlsen surpass Kasparov's record. I was born the same year Kasparov won his title, and now I've seen Carlsen beat his rating record. I'll probably see someone beat Carlsen's record when I'm in my 50's or 60's. Unfortunately, I'll have to see thousands of chess.com posts about how there has been no player as great as Whoever.

I see 2900 not only possible...but only a matter of time. 3000? I don't see that in my crystal ball. His strong performance against the current crop of competition, suggests IMHO that he will be WCC and hold the #1 position for quite some time...maybe 10 years.
"if he beats Anand 9 times, he would reach 3003"
If someone decided that every win against Anand gave him 14 points instead of 4 that would be correct.
Actually, the exact numbers are these: a win against Anand gives Carlsen 3.7 points, a draw loses him 1.3 points, and a loss would cost him 6.3 points. So if every four games against Anand results in a win and three draws for Carlsen he loses rating points.
3000 is just impossible. Carlsen has had one performance around 3000 the last five years, if he can stay around 2880 it would be impressive enough.
Anand is one of the three-four greatest players of the last decades, but he has never once had a 2900 performance in his career. That says something about how difficult it is to perform 2900 in one single event.

If the rest of the top GMs could raise their game a bit, Carlsen would reach 3000 without difficulty. Then chess would really catch the eye in the "real" world.

Carlsen reaching 10000 would not even be enough for chess to "catch the eye in the real world". The problem is not Carlsen, but "chess"....just not structured as a spectator sport.
I think it is technically possible for Carlsen to reach 3000...but for that to happen a "perfect storm" would need to occur. There would be a whole number of events that would need to take place simultaneously. For starters the number of players above 2800 will need to increase drastically...and even then...Carlsen would need to perform like Rybka on steroids to hit the big 3000.
In reality the older players like Anand and Kramnik are on their way down. The players on the way up would be Caruana, Karjakin, Nakamura, Grischuk and other younger players...but how many together will reach and remain above 2800? I don't think the strength base is currently there for Carlsen to reach 3000 and performing at 70%.
"Anand should probably be thankful he wasn't in the Candidates!"
With four Russian players in the Candidates they still maybe missed the best one.