I think what you are asking is - can you trunk the four AP's to increase bandwidth.
Essentially you can have four runnning off a hub or switch with a single uplink. No problems here at all. Only one packet can use the uplink at any one time so you are never going to get the full benefit of the core swich connection.
You will also need to make sure that your AP's don't overlap.
We ahve also tried true trunking on external links, aggregating three point to point links into a switch using etherchannel - thereby achieving 33Mbps on an external link. Tricky but possible.
