From the PL website:
"Changes for broadcast selections
The first changes take place when the League’s UK broadcast partners announce their opening group of live TV matches. This happens in early July and contains broadcast alterations for the first two months of the season (August and September).
TV matches for October and November should be confirmed and announced in early August. For fixtures from December onwards, live TV matches are mostly confirmed on a month-by-month basis.
The Premier League will seek to confirm live TV matches approximately five or six weeks before the start of the month in question. For example, December selections are typically confirmed in mid-October.
The broadcast selections for the season’s final round of fixtures on 21 May, 2017, are usually announced after every club have completed 37 matches. As these matches always kick off simultaneously, there is no direct impact on match-going fans, in terms of rearranged dates or kick-off times."
So by my reckoning they should be either today or tomorrow as Saturday is 5 weeks. They've typically given themselves a bit of wriggle room by saying "will seek to" rather than just "will", though!