I guess they finally realized that .3 content patches for expansions rarely are worth the time and effort they put into them. Let's be real, the second year of each expansion is most often worn out, saw already a massive loss of subscribers and general interest for that expansion. It just makes sense to try to shorten that gap (somehow) and allocate ressources differently.
An expansion really doesn't need three content patches in my opinion, especially not when they only last for 18-20 months (which will hopefully be the average for the next three).