For the ESPP, preferential tax treatment is given for 2 years after the beginning of the offer period, not purchase date (you have to have at least one year from the end of the offer period to get long term capital gains tax, and at least 2 years from beginning of offer period to avoid a disqualifying disposition).

Your ESPP's will require you to pay ordinary income tax on the 15% discount, so you're probably just better off selling your RSU's. Given carry-forward losses, it really doesn't matter that much unless you know you'll be in a higher or lower tax capital gains bracket next year.