Well, I'm pretty sure it is inevitable that the school will re-open... considering that the books are numbered in increasing order of the school year (i.e. Year 1, Year 2, Year 3...Year 7). It's just a matter of whether Harry will decide to attend school, or not. Now don't jump to the conclusion that McGonagal will be Headmistress, since that's not set it stone yet.
It's interesting that you bring up the matter of who's gonna teach Harry, because his mentor Dumbledore is dead ...but Dumbledore claimed that he taught Harry everything he needs to know. But should we accept this on its surface? Maybe Dumbledore is expecting (in death) that Harry should seek a further source of advice. If this is true, then Dumbledore was clearly the foundation of what Harry needs to know before proceeding to Voldemort.
"His current level of skill" is kinda vague. Err.. what kind of skill? Magicial skill? Dumbledore confirmed to Harry that he has a power that the Dark Lord knows not, which is love. Love is a very abstract thing, of course, so who's gonna help Harry understand what this really is? Let's rule out Snape here, he's definitely not coming back, with the Aurors trying to find him for obvious reasons - plus Harry hates him. No, I don't think the answer lies with any of the present Hogwarts teachers... he's probably going to learn through his quest. He will uncover things as he tries to find the remaining Horcruxes. NOT that he won't get help though, he definitely will, and I agree with Sargent_Peach that Fawkes is a definite must among his friends.
Hmm.. I was thinking along the lines of Dumbledore's standalone behavior during his final years.. (I'm not trying to imply that he was losing his marbles
) Remember how one day Marvolo Gaunt's Ring was on Dumbledore's table, and the next it was not? I wonder what Dumbledore did with the ring. He obviously destoryed the piece of soul the Horcrux contained, but why is he not telling Harry how? Surely the answer is not too delicate for Harry's precious ears.