24 hour point total: ~ 1,319,217,040
There are three release weeks of class towers, of which skill and mutant are active now. Assuming players score similar amounts of points for all six towers, to reach the top milestone of 5.25 billion points requires scoring 875 million points per tower, or 1.75 billion in each week of two towers. We're well on our way to that.
As usual, there was a blast of points out of the gate, but things eventually settled down in the range of 15-30 million points per hour. That's still a lot relative to the (higher) milestones. We really only need to average about 5 million points per hour to hit those. So at the moment, I am not worried about hitting the top milestone. We'll see how the scoring continues, but barring a catastrophic drop in points I think we're reasonably safe.
Doubly so because of the structure of the towers event. Players can *literally* get a ton of reward for free just by entering the towers, and not even doing anything. You are instantly leveled up to a floor consistent with your roster strength, which means you can score a whole bunch of points doing literally nothing. I have a Paragon alt that scored something like 5k points just by entering both towers.
The big question now is: how hard is it to reach the qualifying points to get that reward, when the community finally unlocks it. The solo prerequisite score is 35000 points. You get ten points per floor (i.e. per fight), so this requires 3500 floors. Divide by six, and assuming a player reaches the same floor in all six towers, that requires 584 points per tower.
Floor 584 is reached somewhere in the middle of block 76 (its fight #13 in block 76). So assuming a player has a perfectly even strength roster, qualifying for the top milestone rewards requires getting to the middle of block 76 in all six towers. Of course, not many players have that perfectly even roster so most players will likely get higher in some towers than others, but that's a reasonable rule of thumb: you probably need to be able to get to block 76 (and complete fights in it) to reach the top milestone. Fortunately (?) Block 76 is a very long, but relatively weak block. Block 76 is 30 floors of CR 200 fights. So if you can reach it, you'll probably do fine bringing down about a dozen fights in there.
The wild card is that we can also score points from twitch drops. However, we don't know yet how many points will be available in twitch drops.
There's probably a lot of players that haven't really dived in yet. My current rating is 1104 and as I write this my rank is 3154. It was as low as 1300 at one point yesterday, and there's probably several thousand players that will overtake 1100 soon enough. In between arena grinding I will probably try to push my score as high as I can, just to see where I end up on the leaderboard. That 100,000 radiance at rank 1500 and higher is pretty juicy, but honestly even the 75k for top 1% is pretty good. If I actually put some effort into it, I think I can land somewhere around there. That will depend in large part on whether my roster holds out against some of the stronger CR blocks.
If anyone wants a preview of the difficulty of the higher rooms, here's a summary of how many fights and what CR they are for blocks 60 through 80:

No, I didn't scribble down the defender for every single fight. Go watch Seatin's stream for that. He got I think to block 90 before calling it a day. Seatin started in block 64. I started in block 61. That's the approximate difference between a veteran minnow and a content creation cetacean.
Note: my Paragon alt started in block 50 on the skill tower and block 57 in the mutant tower. So it is possible starting block is not a blanket prestige thing, but a calculation based on the strength of your roster in that specific class.