Sit tight for a little while, if nothing else the price of XX cassettes and shifters is absolutely laughable, and mine seems to be wearing just as quickly as an XTR cassette.
Once SLX/X.7 are available I think it would make a lot of sense, you should be fine with your current chainring, the 11-36 cassette gives a really wide range, would go nicely with a 34/36 chainring I'd say.
According to the Madison website SLX 10 speed 11-36 cassettes and pairs of pods are due on the 19th July, so not too long to wait! RH only pods are due 26th July. Sensible prices too, £50 for the cassette, and £30 for the RH shifter, reckon that'll convince a lot of people to shift when stuff's worn out.