an infinite amount of mathematicians walk into a bar. The first orders 1 pint, the next 1/2 a pint, the 3rd 1/4 etc. eventually the barman gives them 2 pints and says "you mathematicians don't know your limits"
That depends greatly on your definition of mathematician. Should we, instead, treat a mathematician now as distinct from a similarly shaped mathematician at a future point, over any interval of time, what might be considered a single mathematician could be considered a set of mathematicians of infinite cardinality.
Linguistically, I think it's hard to justify the idea that the present tense refers to future mathematicians. And even if you did, you'd need infinite time to produce them. I don't think there are any respectable scientists claiming that the human race will survive for ever.