Short version: GW looks really good, and needs a couple small tweaks and not a complete overall, and spending for top tier is not a bad thing.
Full version (buckle up):
Hopefully I don't alienate too many (including my own guild-mates), but I don't see all of this as horrible or the end of the world. Further, I actually see this as reasonable and expected, so I'll try to play devil's advocate. F2P games are always funded by some whales, so as @Sirrian mentioned, having a way to monetize this is necessary to keep the game going. I've played in a few other games competitively, and also developed/published games. There is always this tough balance, and there does end up being a disparity between the very top and a second tier of "competitive free players". It's an ugly reality that developers need to eat too.
So when I saw the huge jump between level 4 and 5 costs, I actually think it is a good design. A "gentler" curve/increase would mean that there would be quite a few "tweener" guilds, around the same level but some spend and some don't. The current system with the big jump almost creates an actual wall, so you're deciding what level to compete for based on your investment.
Now it's not all roses though. While I can understand this scaling system for the sentinels, only the top 10 rewards have been given. The majority of us simply won't compete at that level, so the interesting comparision/decision will be what are the rewards for say guilds 20-50, compared to the costs of either just level 3 or level 4. Assuming those are reasonable, I don't mind competing in AAA rather than the majors.
And that leads to my second big issue, which others have already highlighted. I think that one big bracket is a mistake and not much fun, because it will both pair guilds that have no business playing each other, and it fails to create the friendly rivalry we currently have between certain similar ranked guilds (and would take away my guilds ability to continue to dominate Mean Machines every week ). Not being competitive removes the lower guilds, and lack of known opponents removes the higher guilds.
While I understand adding new features this late would be costly and problematic, hopefully there is a "middle" solution that addresses some of these issues. As it is, I think GW looks really great, but it will ostracize the majority of the guilds and simply not be played by the majority. I do have some practical ideas on how to solve this if you're interested (just not sure if you are, and/or if you've figured out legal yet), just message me.
Hopefully you just mean competitively. From previous previews, just for participating (even not spending) will get you some rewards, and I'd like the new cards So sign us up even if we don't play...
Also, as far as "gambling on other players", I'm no gamble . Right now guilds already have to do this on new members, and figure out who are the leeches and who are the contributors, and take some risks. I think this just adds another dimension to it, but not one that should be considered truly problematic.