Tennis, like fencing, is getting taller at the pro level. However, the athletes in both games are a lot more about agility than bulk. Above 2 meters in height, there aren't a lot of people (and many of the athletic ones end up playing for the NBA), so I would assume that there is room for "normal-sized" people in tennis for a while.

This article has some data on the historical height of Wimbledon champions: https://www.topendsports.com/sport/tennis/anthropometry-wimb...

Height has risen over time, although the rise is far more pronounced for women than for men.

Perhaps most interesting though is the apparent decrease in height variance from the 1990s onwards. Before that, you had a mix of relatively tall and relatively short champions. But from 1990 onwards, which would seem to coincide with the decline of wooden rackets and the rise of the modern power game, you stopped seeing any champions below 180cm.

It's also worth considering that, even if height confers a significant advantage, its impact is limited by the normal distribution of height in the overall population. Assuming that A) you still need to have exceptional tennis playing ability to become a champion and B) exceptional tennis playing ability is very rare and not correlated with height, then you would expect rather more exceptional players of average height than exceptional players of significantly above average height.

So even if height provided an advantage with no meaningful upper limit, you still might not expect champions of 7'0" because there are just no players with such an unlikely combination of extreme height and extreme ability. You might instead expect a statistical sweet spot where the populations of players with both attributes is large enough that the overlap is where most champions sit.