I actually think Wesker wanted Chris and Jill to get into the lab and survive, so there'd be witnesses of his "death" (he purposely let the tyrant impale him so it would look like he was dead). He probably asked Barry to lead them into the labs, but not before Wesker was ready.
Wesker was planning to enter a rival organization to Umbrella by handing them the Tyrant 002. When he woke up, the tyrant was appearently dead and he couldn't extract it's combat data because Sergei locked his access. Without much time left, he had to hurry before the facility exploded, not having time to extract the tyrant (and not realising it was still alive) or finding a way to break into the informatic system.
My theory is that Wesker was planning to enter directly into a leading position in the Third Organization, but due to his failure to retrieve the tyrant made him lose that opportunity, all because Chris set up the self destruction mechanism.
Although the Third Organization still allowed Wesker to work for them (because he still collected precious samples and data) he had to regain their trust (he did that by obtaining the G virus and the backup of Umbrella's data). He never forgot that Chris (and the surviving STARS) was the one who ruined his plans, with his hate growing stronger everytime their paths crossed.