It all depends on the offering of Hyper-V within the next two years.
Think of an IT dept justifying the opex of VMWare when Server 2008 (which incidentally they've just convinced the business to roll to) is happily sitting there with Hyper-V waiting to be utilised. Could be difficult.
Server 2008 hasn't really taken off at the moment, but with lifecycle management and when XenApp 5.0 gets released (read, Server 2008 terminal services support) things will undoubtedly get moving.
When it comes to commoditisation, Microsoft are the daddies and with both them and Citrix working together in the virtualisation market, it's potentially there for the taking.
Also worthy of note is that EMC are one of the most despised companies in the business. Yes, Joe Tucci is turning them around and they are a behemoth but... y'know, it sticks.
I'm all for VMWare VI, it's an amazing product set but it's not an institution. If I can save ~4k per host on licensing and support I will.