In-Stat says that WLAN switches will become more prevalent, but not as stand-alone devices: As Mobile Pipeline explains it, Ethernet switches will increasingly incorporate WLAN functions making the use of thin access points (most radio intelligence) a given but the centralized functions won't require specialized hardware. The article specifically notes that Aruba and Trapeze may face difficulties on their own; Airespace was acquired by Cisco.
There's another course for Aruba and Trapeze and similar companies to take, one that I think we're seeing the early directions toward. Instead of selling centralized hardware and specialized APs, move to centralized software that runs on commodity PCs that integrators and VARs can configure. The value would move entirely to the switching software. Aruba and Trapeze's SLAPP proposal is one step in that direction for removing specialized requirements from APs; the next step would be to agree on a standard featureset with extensions that could loaded by individual switches.