Bitcoin Core exists to solve the global consensus problem. Global network consensus means that there is global network recognition that a particular transaction has occurred and is irreversible. Systems like hub-and-spoke, payment channels, Lightning, etc. are useful, but they are not solutions to the global consensus problem, because they do not meet this definition of global consensus.
Let us focus our efforts on the goal of making Bitcoin Core the best solution to the global consensus problem. Let us address Peter Todd’s requirements to raise the block size limit to 8MB:
1) Run a successful test-net with 8MB blocks and show that the network works and small miners are not unduly disadvantaged
2) Address Peter Todd's concern: “without scarcity of blockchain space there is no reason to think that transaction fees won’t fall to the marginal cost of including a transaction, which doesn’t leave anything to pay for proof-of-work security”
Regarding 1: This is not done yet, though it seems reasonable enough to do.
Regarding 2: It is a fallacy to believe that artificially constraining capacity of Bitcoin Core below the limits of technology will lead to increased fees and therefore lead to sufficient security in the far-future. Constraining capacity below the limits of technology will ultimately only drive users seeking global consensus to solutions other than Bitcoin Core, perhaps through a fork.
Demand for user access to high-capacity global consensus is real, and the technology exists to deliver it; if we don't meet that demand in Bitcoin Core, it's inevitably going to get met through some other product. Let's not let that happen. Let's keep Bitcoin Core the best solution to the global consensus problem.
Thoughts? Is there anything else not mentioned above which anyone would like done in order to raise the block size to a static 8 MB?