I agree that there may be a change in trends but don't think it's down to the MMr remake announcement (although this will potentially have some effect on a handful of titles), if anything it will be as stated above due to a saturation of new titles but there will always be people who want to get their hands on highly rated older machines or classics, just because something is new does not necessarily make it good or a keeper, there are two AC/DC's up on the bay atm and those are recent top titles (neither have been nabbed in any rush), I recently shifted my Spidey over my Congo,
BOP and JM, it's all down to what tickles your fancy.
The thing that recent Sterns or probably most Sterns don't have is nostalgia so apart from gameplay there is nothing else making them a keeper, that is where the classics have an upper hand and the reason why most will maintain their market value.
Space constraints forcing the sale of a machine is always a factor, I would have thought that this would force out the runts rather than top titles and the release of funds needed to finance a NIB forcing the sale of a trophy or newer Sterns (what seems to be happening at the moment with owners parting with recent Stern titles to aquire newer Stern titles or the alternatives, Predator, Hobbit etc)
I think what we have to remember is that the manufacturers hold the sales data, they are the ones who look at charts to see which way the wind is blowing and respond accordingly, if they are churning out machines it must be apparent that it's a worthwhile venture and the interest is there in the same way as Williams bailed out because of the opposite trend.