As previously mentioned, there is a possibility that SPX and RUT may rebound.
For other signs that this rebound will last, I will also watch out for the following 2 ETF (the SMH and KBE)
The KBE is an ETF that tracks the KBW Bank Index while the SMH tracks Semicon companies.
Both ETFs are important and provide insights to the overall economy. After all, will there be a recovery if the banks and semi-conductors companies are not performing well?