It's hot, but is that overheating? What's the spec on the chips? TJMax will be probably be 100-105c.
Read the post again. The memory is hitting 88 degrees but the core temp is still only 48 degrees. That's the "overheating" concern. It could signal a problem with the cooling, the card design or some other issue.
Or maybe it's nothing and the memory just runs hot in these cards.
Only a couple of days to wait until the reviews. But usually issues like these only show up when the consumer gets their hands on the cards.