I agree that if the performances don't pick up, then he'll be gone at the end of the season and he might well be gone even if performances do pick up.
However, I think this comment that he has signed so many players and spent so much is, although factual, still a little misleading. Let's look at the players he has signed:
TBH - Not a success and as such he hasn't featured much of late but was supposedly good enough for Mourinho to sign. A risky purchase that hasn't really contributed anything.
Jo - Probably not Hughes' buy and hasn't yet settled to the premiership and thus hasn't contributed anything either.
Kompany - An excellent buy and at a reasonable price too. Unfortunately the pluses that he has brought to the team have been pretty much negated by the continuing absence of Johnson and the fact that Hamann (who provided us with much stability in midfield last year) has played a season too far.
SWP - Again a good buy but any positives from a pacy right winger have been negated by losing our pacy left winger and IMO, player of the season last year.
Robinho - A definite plus and I'm delighted to have him at City but perhaps at times makes the team a little unbalanced.
Zabaleta - Quality full back as was Corluka, so they cancel each other out.
Bridge - Not played yet.
You said 8 and I have only come up with 7 so I guess I'm leaving someone out but my point remains the same. There has been one bad buy that can really be attributed to Hughes (and that's TBH) and one where the blame perhaps lies elsewhere (Jo - although the optimist in me still has hope). Other buys have basically been cancelled out by injuries and sales to players in the same or similar positions.
So IMO Hughes has got pretty much a squad of similar ability to the squad of last season plus Robinho. Therefore while I would have expected results to have been a bit better than what we have seen so far, I wasn't expecting too much more from a team that surrendered all too easily last season. Hughes took over at a difficult time when team morale was supposedly low and our squad is/was quite unbalanced with a lack of ball winning ability, leadership and no real fit striker of any quality. These are the issues that I would expect Hughes to address in this window if he wishes to keep his job.
From a negative viewpoint, the thing that has surprised me most is our lack of organization, closing down of payers/tackling and work rate when we aren't in possession. This was one area where I thought Hughes would really improve us and that just hasn't happened. Some of his tactical decisions have also been somewhat baffling.
All in all, I think he has done just about OK and no more than that. If he address our major problems during this window, as well as on the training ground, I would expect to see us finish around 8th place which would be a reasonable achievement, though one which is unlikely to keep him in the job I feel.