Well its early days yet, 4E plans are still in the pre-production phase.
But it seems to me that the problem with the template system is twofold.
1a. You need to explain mortal class progression for every class to an infinite degree.
1b. Which means not only more work, but ultimately, a bland and drab standardised epic progression (as we have in the current ELH).
2. Immortal Power/Levels (whatever you want to call it) need to be more powerful than mortal levels. If mortal power continues infinitely, then you have a schism of sorts which warps the relevance of the d20.
The solution appears (at this early stage) to be a slight railroading of 30+ levels into an immortal 'class'.
This means we can ramp up immortal power, but at the same time keep the d20 roll relevant for longer, which is something that really escapes us far too quickly in 3E.
So even if a time lord is only level 100 (and I'm pulling numbers out of thin air here) it might hold the power equivalent to 2000 mortal levels, but without the need to have 999 Hit Dice which is a number which then filters down into everything else - BAB, Saves etc.