I'll see if we can do a quick
Fermi Estimation to take a stab at the answer.
1. Sundance get around 2,000 entries per year of indie films
[SUP]Ref[/SUP]
2. I'll guess that about half of films get submitted.
3. About 7% of the around 200 films with a theatrical release in the USA in 2010 was a remake
[SUP]Ref[/SUP] .. although none seemed to be a remake of a obscure indie film.
4. So let's say that 1 in 5 years have a film that is a big budget remake of an obscure indie film. That seems high (especially since we are all having trouble thinking of examples) but it's just an estimation.
This gives a guesstimate of 1 in 20,000 - about 0.005% as an
upper limit.
Of course, there are other paths - some passion projects were done as short films first and later developed into TV series. An obvious recent example is 'Wilfred' - done initially as a low budget short and then developed later into a TV series.