It's quite possible, Alex from GTANET emailed him and asked him whether or not he would return, in his reply, Lazlow stated this:
thanks for the email.
the answer to your question is simple.
i'll leave it at that.
So maybe he will, if the answer is simple then I take that to mean that he will return in San Andreas
thats right, SA is set before GTA3 so here is what I think..
On the end of the VROCK CD you here Lazlow getting kicked off the rock station (Lazlow talks about getting kicked off it when he is hosting Chatterbox on GTA3) So he may well be on a chat station similar to chatterbox, or maybe another rock station
his personality doesn'y really suit another type of radio