Your take may not be as safe, but seems more realistic and not overly optimistic.Just one by one:
Albies - he's not going to hit 50 HRs, but it no longer unlikely he hits 20. He's proved the concept of power and XBH ability. So somewhere between last year and this year's start, which is a well above average hitter.
Acuna - He's crushing every ball he touches and if anything seems a little unlucky at this point. The Ks are at 27%, and they could go either way. We'll have to wait and see what pitchers have for him second time around the league.
Freeman - He's been better than last year's final numbers, but nothing about his star looks like a seriously hot streak. It's been slow and steady and injury would by your one concern here.
Markakis - sure, he isn't hitting .330 with 25 HRs. But there isn't any real reason to expect his re-found power to go completely away and he's been a fairly steady performer. This should regress, but we should be looking at something maybe a little better than last year to finish and that should have him with one of his best seasons to date. Injury again being a concern.
Flowers/Ruiz - I think expecting similar production here is entirely reasonable.
Flaherty/Bautista/Camargo - Overall production here hasn't really been that great despite Flaherty's start. If this position is upgraded, as it should be, then you should expect better production. If it isn't, there is still a reasonable chance that you get more out of it going forward than you have so far in May.
Swanson - Going from a 60 wRC+ to a 107 wRC+ is certainly a big swing, but I'm not sure that makes it unsustainable. Who is this guy Swanson? Is he the the guy he's shown twice in shorter stints, or is he the worst hitting regular in baseball? I'd lean towards him being something average or better at the plate and his defense took a major step forward.
All in all, I think this groups profiles as still above average even accounting for hot starts. But best in the majors is probably asking way too much.
That will put more stress on pitching staff that thus far has been up to the challenge as run production has gotten a little more iffy.
Much more worried about Newcomb being an Ace holding up than the hitting.