On my Tab 3 8.0 4.2 seems stable with no issues and working well for me. Unless there is a major performance enhancement, I could care less about an update. Samsung has a rep for late updates, so I would not stress over it. Had a Nexus 7 original, much prefer the 8.0 screen size and SD card slot of the Tab 3; a better trade-off IMO versus 4.3.
Hoping it gets at least 4.3. I agree with Trankster, 8.0 screen size is more desirable and it's performance is pretty smooth and stable. The Nexus 7 has quite become the benchmark for android tabs. Unfortunately nexus 7 is unavailable in most countries which makes the tab 8.0 the best option available.