It will not. But looking at what exploits normally do - that would be uncommon and targeted. A lot of common stuff will only drop a stage 2 downloader and try to execute it. Doesn't work - move to the next target.
For most of automated exploitation, selinux is perfectly capable of intervening.
I saw no 0-day exploits to date which are stopped by SELinux. For example, a trojan can use apache process as malware host, without reading/writing to disk at all. SELinux will not stop that even in theory.