Sony Ericsson see RSS as being an important technology for mobile - the Feature has a piece on it too.
Certainly there are lots of applications which could benefit from pushing updating content to users - but right now the economics of mobile internet access are different from those on the fixed Internet (where flat rate is the norm these days). When I'm paying for every byte that I transfer, then I emphatically don't want a service which is polling regularly on the off-chance that updates have occurred... I want a service which pushes stuff at me as and when it becomes available.
There are some great ways of pushing stuff out on mobiles - think SMS or its geeky yet popular cousin, WAP Push - which just don't exist on the fixed internet.
So whilst I'm dead keen to see the principles behind RSS brought to mobile... there might be better ways of achieving this. On the other hand, maybe bandwidth-greedy RSS is just the sort of thing operators want to see more of ;)