It doesn't add much to the odds at all as there is just as likely of a chance that this isn't the case. For all you know it could be the atheists who held off accepting any God who are the one's to get to go to heaven.
Furthermore, If there is a god, he might punish those who believed in a false god more severely than those who believed in no god. In which case, betting on theism would add a potential excess punishment probability.
Actually, this inspires me to me make an equation.
Aknerd's Equation m
(h/n - ( E f(i))) - c*v)*q - a*ya + t*yt = w
i=1
Where:
h = pleasure gained from heaven (in your chosen religion)
n = number of religions that have exclusive heaven
f(i) = pain gained from hell in the i-th religion that has a hell (think of it as a function).
m = the number of religions that have a hell (not including your religion)
c = the likelihood that you will go your religion's hell
v = the pain gained in your hell
q = likelihood that there is a god at all, or at least one that punishes/rewards belief
a = the pleasure gained per year by being an atheist
ya= how long you expect to live as an atheist
t = the pleasure gained per year by being a theist
yt= how long you expect to live as a theist
(due to type limitations, all multiplication is denoted by the *, if two letters are next to each other, the second is a subscript)
The E is part of sum notation. It means you add up the values obtained from i=1 to i=m (I hope the spacing worked out...)
For example, if if we let Calvinism be the first religion, then f(1) would represent the pain endured in Calvinism hell. In order to complete the sum equation, you have to add up the pain gained in all the hells (1-m)
If w is greater than zero, then you are better off as a theist. If not, then an atheist. You simply replace all the variables with numbers that you feel are accurate for some reason.
This equation assumes all religions have equal probability for being true. If you believe that this is not the case, the equation is pretty easy to edit.
Notice that there are only two positive values: h/n and t*yt. This means you don't have to be super accurate with your values. You'll probably get a value near positive infinity, negative infinity, or slightly less than zero.
For me, q is very near zero, and t*yt<a*ya. So, I am an atheist.
I'm sure there are other equations out there very similar to mine. I just kind of made this up on the spot, so if you see any errors, please do tell.