It's now being reported that the EOS Rc will have a full-frame sensor of “about 11.25mp”. For the record, the soon-to-be-launched 4K capable Sony a7S III is 12.1mp.
To me, this looks like it could be the rumored Cinema EOS C50, which is expected to be announced sometime this year. Though the EOS C50 will use the Super35 sensor from the Cinema EOS C200.
I have not personally heard anything directly about an ‘EOS Rc', so please take this information with a big grain of salt.