So much wishful thinking! There is about zero chance any of these things will happen in 2014.
Broadwell production starts in May-July, so for september Apple will have a lot of Broadwell chips. More - nVidia will be ramping up production by now, of the Maxwell GPUs. So we can expect september release of MBP's. If not - october and november are either good moments for release new MBPs in 2014.
GTX850M GDDR5 will be way faster than GT750M. 100-120% inreased performance. Especially in games.People are saying that the change from the GDDR5 modified version of the 750M to the 850M is not that great, but keep in mind that if Apple tinkers with the GPU as it did with the 750M, I think it'll be closer to the 860M.