I think that Darlorich raises an interesting point.
Personally, I think that there's certainly a market for some form of differentiation between accommodations, which would benefit both the customer in terms of providing an enhanced/reduced service as befits their needs, and the train operator who could maximise revenue off the back of it.
As things stand currently, abolishing 1st class completely across the network would be a no-no in my opinion. To mitigate the loss of revenue from the current 1st class offering, you would have to upgrade the current level of standard class accommodation to a level that would attract at least some of the erstwhile 1st class customers. I'm thinking better layouts, with more tables with power points for charging laptops/mobiles (yes, it is happening, but slowly).
Unfortunately, the capacity to make the whole network a one class system just doesn't exist - and it's not just a matter of putting new seats into 1st class vehicles either.
Also, I look to other rail networks around the world, & whilst many aren't directly comparable to the UK network, I see very few that don't offer any form of class system, allowing customers to pay extra for more space etc. The Austrian system seems to be similar, in that 1st class is generally only offered on Inter City & long distance services, with most (all?) regional and urban operations being one class (and a pretty good one too).
There's a couple of other threads open currently, discussing the virtues, (or otherwise) of 1st class travel - unfortunately I don't have the ability to reply to all of them at present due to restricted internet access (long story). In my book though, there would be little to stop an operator introducing a two tier standard class service, where customers could pay extra for an enhanced service (say guaranteed seats/additional legroom/light catering) but provide the same standard of accommodation throughout the train. I'm thinking "Silver Standard" (for those who can remember that far back) and the Open Access operation on the east coast as a possible case in point?