Uncanny X-Men #284 is more literate than I was expecting. It opens with a potted summary of the dispute between Japan and Russia over Sakhalin. Some Russians, and then Sunfire, and then the X-Men all deal with this threat there, which turns out to be a kind of portal into a pocket universe occupied by human-looking aliens with boring factional disputes which turns out to be in danger of colliding into our world, destroying both (shades of Hickman's Avengers), and in which Colossus is heralded as a Messiah (shades of Whedon's Unstoppable).
This is all set-up for the real reveal, at the end of #285, where we meet Colossus's brother, Mikhail, who has been stuck in this dimension for some unspecified but long time. He'd been mentioned in Uncanny #99, as having died in a space launch accident. In #286 we find that was a cover-up, to conceal the fact that the Soviet government know that Mikhail was a mutant. This is not really satisfactorily handled, and the only honest emotional beat that's comes near to the issue is Mikhail's surprise at having a sister, and Colossus's genuine inability to explain the horrors to which she has been subject. There's all sorts of fridge logic that you can apply to this, but it's just the first issue of Mikhail's "return", and none of it is harsher than the point that surely we should have had some more significant mention of Mikhail in the last few issues if we're now expected to buy it as a big deal. I imagine half the readership at this point didn't even know he was an existing (of sorts) character.
The B-plot is the adventures of Bishop. Like it's done before, an X-Men title is here anticipating a successful live-action time travel series. Unfortunately, rather than anticipating something like Terminator 2 again, here it brings us Time Trax, a couple of years early. Oh well.