Nothing other than a parallel universe can explain the appearance of a second lifeboat containing castaway-looking versions of Wyatt and Lucy. Was it piloted by another version of the late Rufus?
I read some old theory some time ago and it claimed that some of the dreams are projections from the alternate universe. If they'll feel too real, they might be you seeing through the eyes of the other you and if they come back as deja-vu's, your soul is more connected to the stream-of-time than you might have ever guessed. I personally don't think that the other life-boat is from a parallel universe, but they're actually going to show us the future, because if you rewatch the final scene, there was line thrown by Mason, "It looks upgraded."
Although "upgraded" can be from a parallel universe, where the engineers were a bitter better than in the prime timeline it's a reach to unknown, because according to the theory every decision you made otherwise, you'll create a new parallel timeline to the original one. Eventually this will mean that there are an infinite number of parallel universes instead of one, where we made opposite decisions and created a so-called mirror world.
Thing is that they've proven time and again in this season to make it absolutely clear that you cannot escape history. The events happens if they're meant to happen regardless Lucy's or Rittenhouse's teams trying to interfere with them. Some things might change but the end is the same. Rufus died and when he bled on the small screen I shed my tears like any other person. I even shouted to the screen for Lucy to "Double Tap" when she her gun on Emma's forehead and I was really glad, when she pulled the trigger. Emma needs to die or she'll create an Empire for herself with everything she has inherited from the "family."
Wyatt also needs to learn to live with the regret or he will never be able to function like the bearded veteran we saw standing on the other lifeboat hatch.
