Not this Congress, not for the foreseeable future. If the ACA were overturned, it wouldn't prompt MORE radical legislation, it would eliminate what we got so far and make healthcare reform radioactive for at least another decade or two.
The only realistic prospect for single-payer is for states to start doing it, then for it to spread. That's how it happened in Canada. States can start going single-payer as early as 2017, which is when Vermont's new system will kick in.