The next Mass Effect game is a fair old way away, but BioWare has at least said what we shouldn't expect, and that's a rehash of Shepard's character.
So, first off, speaking to VG247
BioWare Montreal producer Fabrice Condominas said, “There is one thing we are absolutely sure of – there will be no more Shepard, and the trilogy is over.” Clear on that?
And we won't be getting a Shepard-alike, either. “So first, we don’t want to make ‘Shepard 2′, or Mass Effect 4
with like, ‘oh there’s no more Shepard but you’re a soldier in the universe’. So this will be a very, very different context for sure, and nothing has been decided on the rest.”
Condominas also noted that, thanks to the scope of the ME
universe, "we don’t even know what kind of time frame we’re going to be in". The studio is currently just going through the process of taking on ideas from its development teams.