Based on Riot Mortdog's post, the average value of a leveling capsule is 910 BE, and a Milestone Capsule (every 10 levels) has an average value of 2,120 BE. So let's just add all that up from level 30 to 175... 148890 BE. To go from level 30 to 175, you have enough BE for 23 full priced champions.
Clearly we are going to have to level waayyyyy beyond 175 or even 200 to actually unlock everything, which is fine. So what is the XP per level breakdown beyond level 175? Riot Mortdog's poost says "The highest amount of XP to level (from 174-175) is 4600xp." Does that mean XP/level caps at 4600? Maybe... Rito is being intentionally unclear here. Regardless, let's just assume this 4600 XP/level cap.
Again using Riot Mortdog's numbers, under the old system, a 50% win rate on Summoner's Rift game modes meant about 83.5 IP/game (100 for win, 67 for loss). First win of the day could thus be thought of as just under 2 games worth of IP (it's now worth a little bit over 2 games worth of XP, so not much of a difference and we can just ignore it). Anyway, at 83.5 IP/game, it used to take 76 games to earn enough IP to buy a 6300 champion. In addressing whether the new system is better or worse, all you need to do is ask how many games does it take to earn 6300 BE? Well given Riot Mortdog's numbers (2120 at milestone, 910 otherwise), 10 levels (including the milestone capsule) gives on average a total of 10310 BE. That's an average of 1031 BE/level. So to earn 6300 BE, we need on average 6.1 levels. At 4600 XP/level, that is 28109 XP. Again using the numbers Riot Mortdog gave of 250 XP/win and 205 XP/loss, that's 125 games to reach 28109 XP. Apparently, Mortdog gave a clarification that XP/level in the endgame averages out to 3840 XP/level, which means that 6.1 levels is 23424 XP, which means using his numbers of 250 XP/win and 205 XP/loss, it's 103 games to get 6.1 levels.
In other words, at ~level 175, it will take 103 summoner's rift games to have enough BE to buy a 6300 BE champion. And that is assuming the average XP/level caps at 175.
This means that gaining champions in the end game just got 35% harder.