He announced his resignation on Twitter yesterday and is leaving the show (I think he'll be doing Springwatch before going). The BBC tried to axe him two years ago in the interests of diversity but after the viewer outcry they merely changed his role and brought a fourth presenter on, Gillian.
I can't abide Gillian. I've tried but she comes over as all hands and very stilted. Martin is fab and hugely knowledgeable.
I don't think I can watch it without him. I wonder if there is more behind his resignation (ie he does feel he's being pushed out)? Either way, think it a shame.