Why will Casper FFG like be a tailwind for ETH price (expected to be deployed in Fall 2018)?

Here are 4 factors I believe to be significant (ordered by importance):

1. It helps prove full-Proof of Stake could work. Right now, PoS is an implementation risk for Ethereum, but if hybrid PoS-PoW works, it shows that Ethereum's full value proposition of becoming an energy-efficient blockchain may be possible. So far, all has gone well with on test net. This will create additional hype behind Ethereum as a successful project with even more potential. It will also reduce Ethereum's reliance upon mining pools, and the risks that come with them.

2. Mining rewards / supply inflation will plummet. Issuance is expected to drop by 80%, dramatically reducing ETH inflation. It is also possible that burned fees could result in supply deflation, but I wouldn't expect this early on. It also reduces the risk of a 51% PoW attack (which even now is unlikely for ETH).

3. ETH becomes an income producing asset. ETH will generate between 2% and 8% income for validators / stakers. Right now, it looks like they are targeting 5%. This income will come from fees, and if necessary, from modest inflation. Staking pools will soon be in place to allow for staking with any amount, and it's likely big companies (like exchanges and other TBD custodians) may make the staking process very easy for users after some time.

4. Provable lockup of supply. About 10% of ETH supply is expected to be staked at the start. Those ETH must stay locked up for the duration of a staking period (a period of several months). This could reduce market liquidity and help drive up the price. It may also spur a round of buying by individuals and institutions who want to get to the minimum staking amount (1500 ETH at the start).

Bonus Factor: Also, at around the same time, we are likely to see many different types of Plasma implementations as L2, thus adding much needed scaling to the system. I expect this will increase the volume of tokenized assets on Ethereum and overall bring more activity / usability to the Ethereum ecosystem (thus boosting developer and user adoption, and further entrenching network effects).

From where I sit, things are looking pretty good, as an ETH-investor and an Ethereum ecosystem fan. Excited to be here and a part of this community during these eventful times!