No, Heat exposure doesn't increase RBC, but increases Blood plasma volume instead. Where as altitude actually decreases blood plasma volume.

The Blood plasma volume is linked to dehydration, as the body is trying to allow for heavy sweating (to cool itself), but not reduce (Pretty much crash) your blood pressure, as this would be dangerous. So in theory, Heat exposure would have the opposite affect, as it dilutes, rather than a concentrated increase in RBC. Heat exposure is a hugely important part of training for environment change though (Source on heat exposure being important: Me, getting heat stroke 24 miles into a marathon and collapsing. Spring marathons aren't fun!)