Black can choose to retreat to e7 with the bishop, but that also has its nuances.
Wing Gambit against the French
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Jul 24, 2017
0
#4
It looks interesting. However, at the level of strong engines, it's refutable by 4...cxd4 (4...cxb4 is an erroneous move).
P.S. Sorry, I spoke about French with 2. d4 instead of 2. Nf3.
Yigor wrote:
It looks interesting. However, at the level of strong engines, it's refutable by 4...cxd4 (4...cxb4 is an erroneous move).
4...cxd4 is not possible, white only plays d4 after black moves cxb4
Jul 24, 2017
0
#6
Ah yeah, sorry, I looked at French with 2. d4 instead of 2. Nf3. 
In this latter case, I agree with your first variation (8...Ba5) till 10th move where black should play 10...h6 instead of 10...O-O?!
A simple way to meet this with minimal knowledge of theory is 4...b6.
But accepting the gift is fine, if Black knows what he's doing.
Taking ...cxb4 followed by a3 can be pretty annoying for Black if he/she is unprepared but as Pfren underlined it Black is not even forced to take it. What if Black plays ...b6, or ...c4 (which I usually does, followed by ...cxd3 when White plays d4 or d3)?
I´ve recently met this line in youtube. It looks funny to play. After 4.cxb4 5.d4 white stabilize his center, and then plays a3 (similar idea to the Volga)
You can see the dark Bishop is now misplaced. Black must be careful, if he castles now then Bxf7+ and is checkmated.
There are also ideas with Na3 Bxc3 Nb5!?