It may be only two seconds, but points to a couple of things.
Firstly, it's now obvious that Jon will return to Winterfell, where he'd left Sansa as steward of the North while he was off hunting White Walkers and consummating his relationship with Daenerys Targaryen (aka his aunt).
Secondly, Sansa is clearly not happy about the arrival of someone. She's also welcomed back her long-lost siblings Arya and Bran in Jon's absence, so maybe it's the stress of hosting guests with no prior notice in what's rapidly becoming a full house. It's doubtful that Jon's the cause of her side-eye — because the two have been running a fairly formidable team, plus it's him she's hugging— so it's probably aimed at Daenerys (Emilia Clarke) who Jon was last seen sailing to Winterfell with at the end of season seven.
(Also — worth remembering that Tyrion, Dany's right-hand man who'll presumably also show up at Winterfell, is actually Sansa's former husband, so maybe it's a spousal issue? However, given that they parted on good terms and with mutual respect, it's also unlikely.)
It follows reports that the show's return has potentially been pushed back from early to mid-2019.
The HBO preview also featured a first look at True Detective's long-awaited season three, new episodes of The Deuce, Veep and Meryl Streep joining the cast of Big Little Lies season two.