How big is the Mersenne Prime?

Speculation about the latest Mersenne Prime:  How many digits? 
Casting Out Nines plotted the numbers and made a guess of 10.5 million digits.
God Plays Dice likes 14.5 million digits instead.
Now you can play too!

Here's my graph of the known Mersenne Primes.  Where do you think the next one will be?

But wait ... what if we eliminate the first few and concentrate on the later numbers:

 

And, possibly, more insight with this one:

What you are seeing is the M(p) in pink and lines for 11M, 12M, 13M, 14M

I'm liking the 10.5 million or 11 million guess.