Since wave 2 was a flat, I would expect wave 4 to be a , as it's shaping up so far.
Since the start of this bull move from the May 3 low, all corrections have been very shallow. I see no reason for this wave 4 to be any different.
Now, there is a reason for a deeper correction, or possibly the alternate count (mentioned in related post). Possible spinning top candle in SPY Monday, and Gartley sell with bearish doji candle in QQQ Monday puts the bullish count in question.