But...But....If River says that 'she is trying to tell him'. How would River's name (or other such clue) be imparted onto the cot if it was the doctor's cot???
Assuming the cot hasn't been written upon since the doctor used it, then how can it even hint at River's identity??? Unless, of course she is in some way related to him (such as Mummy dearest).
We all know that both the Doctor and River are/were/will be an item but he suddenly gets a revelation and quitely says 'Hello'. He surely wouldn't say that to someone he already knows that he has/had/will have a history with??
Come to think of it, River does call him, My love, and ok, yes she kisses him (albeit once passionately, but lets skip that for this theory anyways) which could, I say,COULD possibly mean that she is somehow related. Does being his 'wife' mean something different in Time-Lord society???
Incest isn't something the show will want to get itself involved with, so maybe the 'Mummy' aspect is wrong, but there is definitely something else to be considered in their relationship.
Just a thought