But unless the cartel has 100% of has power, which is impossible, these transactions would simply wait for an honest miner's block.
This is incorrect. A cartel with a high percentage could,
within the protocol, reject blocks that don't follow its transaction inclusion rules. It doesn't take 100% to completely block some or all transactions from the chain.
On top of this the miner centralization issue is not a long term problem anyway. The system will naturally decentralize over time. With the introduction of ASICS it was difficult to obtain hardware and professional setups had an advantage in procurement only. However centralized mining installations in datacenters naturally are at a cost disadvantage vs. home style setups which have free space and cooling. As the ASIC market matures I think we'll seem a shift back towards more decentralized mining anyway.
This has probably already happened to some extent. The physical (as opposed to pool) mining is
somewhat centralized. It was even during the CPU and GPU eras -- specialists build big mining farms (Satoshi is rumored to have had a pretty nice one), the rest don't. But the early ASIC era when there was only a relatively small quantity of gear in the world that represented the bulk of all of the hash power made matters much worse (when ghash had 50% a large portion of that was their own actual equipment), but only temporarily. That kind of transition will likely never happen again.