I think both players have huge question marks over them. Can Heatley recover even a little of his former offensive flair? He is a one-trick pony (quick, heavy shot) and that shoulder injury may have taken that away for ever. Michalek certainly has more tools, but none of them are as high-end as Heatley's used to be, except for his speed. And with 3 (or is that 4?) major knee operations at his *still young* age is more than a little alarming.
Sure, Michalek looks to have now fully recovered (well, full recovery is probably two years, but he's gone far enough now that he can play through the pain/discomfort at pretty much the same level as before). But will he have an injury-free season next year? And if not, is the next one going to be the one that ends it all?
Heatley, may be showing signs of continuing slow-down, but it also could be other factors (team is generally playing poorly, different lines, reduced minutes).
IMO, it's too early to say with any confidence. What's always been clear, though, is the character.