Guarantee it will be on PC come what may. This is a game that would get 360 owners who are intending to buy PS4 to have a serious rethink. But I also think EA are very disinclined to re-exclusivise this franchise. Timed exclusive, perhaps, exclusive DLC I can see that possibility, exclusive marketing I think you can almost be certain of this.
The cost of going true console exclusive, with the install base lead PS4 currently has, is very high. You have Dragon Age: Inquisition selling best on PS4, so the console WRPG fanbase seems to be gravitating to PS4. Mass Effect will have potentially the bigger fan base on Xb one, given that's where it started, but it is entirely possible that a lot of the Mass Effect fanbase has moved across to PS4. There has to be quite a bit of cross pollination between Dragon Age and Mass Effect.
But really people should be saying no to turning multiplats into exclusives. This is bad. This will only lead Sony to do another SFV type deal and that kind of tit for tat is not what I want to see this generation. Sink money into more exclusive new IP and get the generation humming with exciting new properties that make each console's game library unique. Also doing that means having true exclusives, rather than console/PC exclusives.
With Mass Effect 4 I will just wait until I get a new PC that is capable of running it if it skips PS4. I only buy one console per generation and I have PS4 already.
“The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.” - Bertrand Russell
"When the power of love overcomes the love of power, the world will know peace."
Jimi Hendrix