Corbyn is speaking tomorrow on Brexit, so it could all change again. 
Although I do think he was the 'warm-up act' for the speech tomorrow. Starmer was using very precise language, as I'd expect from a lawyer. Nothing detailed, everything to be negotiated, just paving the way for JC.
There may be a huge majority in parliament for a soft Brexit, but to me this looks like Corbyn trying to force a vote of no confidence in May, using Brexit as the catalyst. I cannot see any Tory voting with him for that - even if they agree with the LP position on Brexit. Anna Soubry, for example, has a majority of 389. She will not vote for anything that could force an election.
Will be very interesting to see how this plays out though.