Anyone else kind of feel bummed out by this? Does it mean no more single player TES games?
No it does not mean that.
Team that Develops the single-player games - Bethesda Game Studios
Team that develops the MMO - Zenimax Online Studios
Two different teams owned by the same parent company, each with their own staff, budget and development goals. Neither directly involved with each other, except for perhaps BGS writers being consulted on lore elements. TES VI is safe, and I'm sure we'll see it come out after Fallout IV, whenever that will be...