There are some compelling reasons to believe that the next move down in risk assets across the globe is about to begin:

First and foremost the Euro a good proxy for global risk appetite has completely broken down despite the perceived resolution to the crisis in Greece. The strong dollar could eventually cause the liquidation of carry trades (Source marketwatch.com):

Next Gold often a proxy for global liquidity has broken down below the major support of 1150.

Oil and base metals like copper which are barometers of global economic strength have had major break downs:

The S and P 500's last few highs have been marked by bearish divergences with non conformations in the transportation index which has not hit new highs in over 8 months:

Finally the Vix is yet to take out it's 52 week lows and is reaching levels that suggest complacency:

Yes marginal new highs in the S&P 500 and other indices are possible but the above developments taken together with unfavorable market cycles into mid August make for a possibility of a global market sell off in the not too distant future.