Stocks appear to be waiting for next week's Fed meeting and Alibaba IPO to make the proposed small-degree 5th wave terminal move. This perspective labels the consolidation since late August as a small-degree 4th wave. See the green count in Chart 1 (SPX) and Chart 2 (NDX).
A competing alternative counts the advance since the August low as complete on September 9th. See the blue count in Chart 1 (SPX) and Chart 2 (NDX). According to this count, the terminal fifth waves have taken on interesting forms.
In SPX, wave five is a rare sideways terminal triangle, which reflects the waning momentum of the advance. Note that the proposed top has failed to make a nominal high in SPX.
In NDX, wave five is a regular impulse which ended at a nominal high. However, the visual structure resembles that of an expanding ending diagonal triangle, another terminal structure.
It's possible to have a leading diagonal triangle decline in SPX and the Dow. See the red count in Chart 1. However, a new high in NDX on September 9th casts doubt on this interpretation.