Don't be so sure that they need to "react" ;) There have been plenty of very decent line-ups recently, even if they're not to everyone's tastes (they're also unlikely to be able to change much at such short notice). I wouldn't particularly see this as a delay - as covered above, it's almost always the Wednesday before the games become available that the announcement goes us. There haven't been many occasions when that would put the announcement actually within the relevant month (i.e., when the 1st falls on a Wednesday) - June 2016 is covered above, but then prior to that you'd need to go back to July 2015, when the announcement (on the US blog, as this was before the EU came into line) was on 1 July. Going back further, the announcement for April 2015 was on Tuesday 31 March. In short, I'd expect the announcement on either Tuesday or Wednesday next week - for it to have been today would have been the outlier.
Just a bit of a waiting game really isn't it, only Sony really know. Hopefully the delay is due to a change in the line up in reaction to GWG :)
The only change I can see is May of last year. When they were announced on a Tuesday (as you say it's always a Wednesday) and that was obviously because the Wednesday fell on the 1st June. Looking at this month. I'd expect them today, or Tuesday the 31st :(
Reasoning seems to be that games are released on the first tuesday of the month, which will be the 7th, and the announcement is the Wednesday before, which on this occasion happens to be the first of the month.
Who's this guy then? Next Wednesday is the 1st. They've never been announced the same month as the release. Always a first, I guess.