Paddy Power has 8/11 for 2020 and 6/4 for 2017, top of my head 20% margin for Paddy Power implied probability of c. 75% for 2020, 15% for 2017.
Sounds about right to me therefore I'm not betting, you disagree then go make yourself some money.
I never said it was impossible, but difficult, for her to call an early election due to the FTPA, so 15% chance of a 2017 election sounds about right - possible but unlikely.
I was countering the impression some posters here appear to have that it is pretty easy and a bit of a foregone conclusion that May will call a 2017 election, in other words turning the likelihood of its head, say a 75% likelihood.
There is a further consideration that goes beyond the logistics of getting turkeys to vote for christmas (in other words persuading MPs who have 3.5 years to go before they have to face an election to opt for one in months with an uncertain outcome). That is that were May to call an election, which would necessarily be dominated by brexit, she would have no option but to clearly lay out her preferred brexit option in a manifesto - simply going brexit means brexit etc simply isn't going to cut it. If the electorate aren't clear on her strategy and think that she is continuing to obfuscate, while wanting their votes, that isn't going to go down at all well. But she desperately doesn't want to reveal her hand, not due to the stated line on negotiation, rather because as soon as she opt for either soft brexit, or hard brexit all hell breaks loose in her own party, with UKIP once again sniffing on the sidelines.