Steam sales won't be as fun without flash sales and daily deals. It might be better, but it won't be as fun.
I think it's fairly easy to predict the consequences of this, and depending on your main perspective, this could be a good thing or a bad thing.
Good for developers and publishers because it puts a bit of a brake on the "race to the bottom" mentality.
Bad for developers and publishers because the hype and momentum that was built by strong user engagement, by keeping people coming back periodically and having a rhythm of buildup and excitement to each new daily/flash deal surely was one of the factors that made each new Steam sale such a breakout success.
Good for the end consumer because the gamification of Steam sales and slight(?) manipulation of certain psychological traits associated with it can be a dangerous road to go down.
Bad for the end consumer because it can be assumed that discounts won't be as steep as before.
I assume Valve has done a lot of testing and predictive modeling on this to arrive at the conclusion that this is the best way to conduct this sale
... or someone just had the spontaneous idea to try it out and see what happens. You never know with the cards at Valve!
At this point, I'd say it's 50/50 whether this is the way sales will be done going forward or if this is done to let the Christmas sale have a bigger impact by being a return to the crowd-pleasing daily/flash model.