I'm planning to FIRE in 2020 too. I've run my numbers through a multitude of retirement planning spreadsheets (my favorite is from Financial Mentor - the Ultimate Retirement Calculator) and no matter how pessimistic I am with inflation or low rates on investments, it looks good.
I like Mr. MM's comments on the 4% SWR blog where he notes that this rule assumes you'll never earn more income, never have a pension and never adjust your spending. That, plus the fact that my husband will likely always work part-time, and we're starting a business that should earn income independently from our hands-on involvement gives me some security. With the indications that the Canadian government is raising the max contribution to our TFSA (tax free savings accounts, for you non-Canucks) from $5500 to $11,000 per person/yr., we'll need to watch our spending and make sure we can contribute the maximum.
As for roadblocks, it's likely to be in the form of unplanned spending on house renovations. Our planned $5000 spend on rebuilding a deck this summer is likely to expand to $10,000 as our initial demolition has revealed some additional damage due to water infiltration (who builds a flat deck without a roof membrane, fer heaven's sake!). However, it'll be money well spent on our enjoyment of the new deck and house value. No, I'm not expecting to recoup 100% of our expenses on increased property value, but the work is a necessity and our DIY skills will keep costs as low as possible. Roof and window replacement is another planned budget item, which has the potential to go sideways - the joys of older home ownership!
So, 2020 it is....!