I was looking thoroughly for the omission of ...c5 in many repertoire books ( Semko & Sakaev-Queen's Gambit Declined 3rd ed., Iakov Neishtadt-The Queen's Gambit Accepted, James Rizzitano-How to beat d4,Raetsky & Chetverik-Starting Out The Queen's Gambit Accepted ) and found absolutely nothing about the pros and cons of delaying this move!
This is rather disappointing as the idea is quite reasonable, and can come to any player rated from 1800 up to 2400 so it should be explained in repertoire books. However, after trudging through the ECO D 1987 I was able to find something:
[Title "Black delays c5 break"]
[fen ""]
1.d4 d5 2.c4 dxc4 3.Nf3 Nf6 4.e3 e6 5.Bxc4 a6 ( 5...Be7 6.O-O O-O 7.Nc3 c5 ( 7...b6 8.Qe2 Bb7 9.e4 $16 ) 8.e4 cxd4 9.Nxd4 Qc7 10.Qe2+/= ) 6.O-O ( 6.Nc3 b5 7.Bd3 Bb7 8.O-O ( 8.Qc2 Nbd7 9.a4 b4 10.Ne4 c5 11.Nxf6+ Nxf6 12.dxc5 Qc7= ) 8...Nbd7 9.e4 b4 10.e5 bxc3 11.exf6+/= ) 6...b5 7.Bd3 Bb7 8.a4! b4 9.Qe2 Nbd7 10.e4 Be7 11.Nbd2 c5 12.e5 Nd5 13.Nc4 $16
In either case White can favorably open the game ( he will have more space and is better developed, also notice that his center is solid and your ...c5 will only free your game but will not give you sufficient counterplay ) and get good attacking chances.
In the main line in the above diagram, you seem to have solid position but do not be fooled. Yes, White has e5 square no more, but you are weak on the c-file since your b-pawn is on b4 where it does nothing useful. White was able to outplay Black by posting knight to c4, which is wonderful square for him. He can also attack on the kingside. Black on the other hand, has no viable counterplay and will probably have to weaken himself further with ...h6 at some point.
As for 6.Nc3 sub-line from the above, you can achieve typical position with isolated pawn after ...c5 at some point, but again White is just so superior in development and has typical space advantage. You lag in development, thus you will need time to organize counter-attack while White can already start creating problems to further delay you, like regrouping pieces for kingside atack.
As for 5...Be7 line, White also has superior development and wonderful centralization of his minor pieces. He has more space and his queen is well posted, unlike yours as she is prone to harassment with Nb5 ideas. You will need to play ...a6 at some point, further losing time which is dangerous if we take White's lead in development and space advantage into account. Black may get playable position but it will be a series of accurate moves and even then White will have at least small advantage.
It seems that this is the point of 5...c5, to ensure Black gets enough space in the center and hinder White from harmoniously developing his pieces, by forcing him to count on entering endgame or simplifications.
This is all I was able to find, if anyone has the latest ECO D I would highly appreciate the update on lines I listed above...
Hopefully this answer helped, as there is nothing else at this moment I can do. Best regards.
