Since there are a lot of people in the clan playing OW competitive and asking when the season ends, I decided to post this here.
Season 4 has it's end date set for May 28 8:00pm EST.
There will be a countdown added to the competitive mode box next patch.
What is interesting is that Scott Mercer (Principle Designer for OW) stated that they chose to have a shorter off season. Typical off season time was around 1 week so we can still expect Season 5 to be up on June 1st.
Source: https://us.battle.net/forums/en/overwat ... 049#post-5
Also of note is that both an Art Book and a collection of the 12 currently released comics for Overwatch will be releasing Oct 24th and Oct 10th respectively. You can find those here.
Already pre-ordered the Collectors Edition Art Book and the Anthology.