Considering Makoun only managed to get 8 starts under Houllier, and only played 4 full games, it's hard to imagine that he developed some deep attachment to Gerard that would mean he just had to leave when GH was gone.
Also, call me a sceptic, but I find the "Cabaye didn't come to Villa because Houllier wasn't staying" story a bit hard to take when you read on to the bit where he says that no-one in the Premier League made an offer until he got a phone call from Alan Pardew, who he didn't know at all but sounded nice on the phone, so he went to Newcastle. Doesn't sound he was as definite as people are making out over which coaches he would or wouldn't play for!