S&P 500 in an expanded flat? - (c) wave coming?

My Elliottwave analysis of the S&P 500 indicates that we might be finishing up wave (b) of an expanded flat that will complete wave 4.

I have come to this analysis because of what looks like a triangle formation in the middle of this latest rally, which indicates a corrective (b) wave.

If correct, a strong selloff is coming imminently.

Comments appreciated.