Critics of Calvinism regard Calvinism as an especially harsh version of exclusivism. They castigate unconditional election and they criticize the Reformed position that regeneration is causally prior to faith. The point of this post is not to defend those tenets directly, but to consider a potential fringe benefit.
i) In traditional evangelical exclusivism, premortem faith in Christ is a prima facie prerequisite of salvation. But there are caveats. That's usually confined to mentally competent individuals. Exceptions are often made for those who lack the cognitive faculties to exercise Christian faith. People below a certain age. People with severe congenital brain damage.
Christians who become senile. Christians with brain cancer. The latter two lose their faith, but they don't lose their salvation. Rather, they lose the cognitive faculties to believe.
That's not necessarily the same thing as declaring all those groups to be heavenbound. Because Scripture doesn't give definitive answers to the salvific status of special cases, some evangelical theologians suspend judgment while others stake out the universal salvation of all who die before the age of reason (to take one example).
ii) Although Scripture attributes salvation to faith in Christ, Scripture also attributes salvation to regeneration. It's lopsided to focus on saving faith to the exclusion of saving regeneration.
iii) According to evangelical freewill theism, faith causes regeneration. According to Calvinism, regeneration (in tandem with the Gospel) causes faith. In Calvinism, regeneration is causally and sometimes temporally prior to saving faith. There can be a chronological gap between regeneration and saving faith. For instance, God can regenerate someone as a young child or even in the womb, but they may not come to faith until they reach the age of reason or later. Likewise, in Calvinism, election is logically/teleologically prior to conception (indeed, prior to time).
iv) Suppose (ex hypothesi) that God regenerates a Muslim with a view to the Muslim coming to Christian faith, only God regenerates the Muslim several years before he comes to faith in Christ. At that stage in the process, the Muslim hasn't been exposed to the Gospel. But suppose the effect of regeneration is to make him doubt or lose faith in Islam. At that stage he lacks an alternative. But regeneration broke through the social conditioning which made Islam unquestionable prior to regeneration. And suppose that prompts him to search for religious alternatives–until he discovers a Bible. Regeneration planted a seed that eventually germinated in faith. But there was some delay.
v) In principle, God might elect or regenerate someone who's killed in a traffic accident before coming to faith in Christ. I wouldn't press that. In general, God coordinates election and regeneration with the Gospel.
That said, I'm not sure how we can rule out the possibility that God elects and regenerates some people who die before coming to Christ. Their faith will be postponed to the afterlife. Indeed, many Calvinists already believe that happens in special cases (see above). Is salvation a matter of lucky timing? If you die a minute before, you're damned?
Ironically, something freewill theists find so objectionable in Calvinism has the potential to make it more magnanimous than traditional evangelical freewill theism. Not something to bank on, but an open question in Reformed theology. By contrast, faith and regeneration are chronologically inseparable in traditional evangelical freewill theism, resulting in a harsher version of exclusivism.