Shows already been renewed for a sixth season by Amazon. I've really enjoyed the show thus far and my only complaint I've had on the previous season is that they spent to long in cave during the flood, other wise it was amazing as the previous seasons. So I'm definitely looking forward to season 5 this december and in the future season 6.
Gotta say I haven't read the books at all but I have heard about the time skip coming soon. And in all honesty I don't see the problem. They've already made small changes to the story here and there (from what I've read) so making another small change; say compressing down the time skip wouldn't change much of anything story wise. Another option would be age the characters with makeup and cgi although that would cost money unlike the former option.