I for one most certainly wouldn't be getting excited at all - yet. There's a long, long way to go, and we're not liable to find out the strength of the evidence until, and if, this does end up in Crown Court. And that might take a heck of a long time.
Until then I'd be extremely cautious, although having said that, the news will probably be heartening to Jo's family who are of course desperate that their daughter's/sister's killer is brought to justice.
It also begs the question about what evidence there was in the first place to arrest the landlord who, as far as I'm aware, is still on Bail. He will presumably either now have his Bail cancelled and no further action taken, or else they may be awaiting the results of further DNA if they believe he still could be implicated.