I'm with tactics.
I see the independent route as the main way forward for the next few years. Grime needs to solidify its own fanbase in the inner city, get people buying mixcds, tshirts, ringtones etc and supporting their own local artists before setting sights on anything else.
But yes, I think JME and Skepta are the most likely to succeed. They're young, charismatic, fun, hard working and both wicked MCs and producers. And I agree, initially I wasnt that interested in JME because of his flow but I actually listen to Derkhead a lot and really enjoy it. 96 Bars of JME with Grime Reaper is a classic, as is the song where he's talking to his mum about the birthday party.