Even the attack have some political implication, I don't think it will convince anybody to fork
Probably not. Bitcoiners are extremely resilient, they don't change their opinions just because of mere facts.
a fork will just make the situation worse.
"Fork" does not mean to increase the blocksize, although changing it would require a fork. (Luke Dashjr wants a fork to
reduce the max block size to 100 kB.)
[ With larger blocks ] Spammers can send millions of 0.0001 bitcoins without any fee to flood the mempool regardless of the blocksize. With a 20MB block, they will quickly raise the average block size to 20MB and heavily slowdown the network. On the contrary, it is safer to stay at current 1MB blocksize, so that spam can be analyzed thoroughly and dealt with
The larger the block size limit, the more expensive a spam attack would be. To be effective, a spam attack must generate more transactions per second than the network can confirm (in addition to its normal traffic). With 1 MB blocks, that would be more than 1.8 transactions per second. With 8 MB blocks, it would be ~21 tx/s, With 20 MB blocks, it would be ~53 tx/s. Only the excess spam above those numbers would accumulate in the queues, creating and feeding the backlog.
More transactions make the attack more expensive. The average transaction fee now is ~0.01 USD/tx, it seems. Assuming an attack with twice the traffic numbers above, the cost would be ~80 USD/h with 1 MB blocks, ~850 USD/h with 8 MB blocks, and ~2100 USD/h with 20 MB blocks.
Also, the larger the block size limit, the faster a backlog will clear out. The goal of the current spam test was to reach 250 MB of unconfirmed transactions (but they got about 70 MB maximum, so far). The backlog will clear at the rate equal to the capacity of the network, minus the current traffic (which is about 30% of the capacity). So, with 1 MB blocks, minus 300 kB per block, it would take ~360 blocks (~2.5 days) to clear 250 MB of backlog. With 8MB blocks, it would take ~33 blocks (~5.5 hours). With 20 MB blocks, it would take ~13 blocks (~2 hours).
Increasing the block size limit to 8 MB or even 20 MB will not make the risk of a spam attack become negligible, because a determined attacker with deep pockets can afford much more than 2100 USD/hour. But it would make the attack 10 times more expensive, and clear any backlog almost 10 times faster.
But the main reason to increase the limit is not to ward of spam attacks (which, as said above, are impossible to avoid). It is only to prevent the network from becoming saturated due to a possible increase in
normal traffic. If the average normal daily traffic gets to about 300'000 tx/day (only 3 times the current value), there will be recurrent "traffic jams" that take several hours to clear. The delays due to traffic jams will drive more users away from bitcoin, until the traffic stops growing. Only users who really need bitcoin (like drug users and ransomware victims) will put up with the jams.
Increasing the block size should have been a no-brainer non-event, a trivial and routine maintenance action to get one possible problem out of the way. It is what any plumber would try to do when he notices that a rain or sewer pipe is about to become insufficient for the flow it is supposed to carry. Unfortunately, the business plan of Blockstream requires
forcing all individuals who now use bitcoin to use their "overlay network" (Sidechains, Lightning Network, whatever) instead. To do that, they must keep the block size limited to 1 MB until the network saturates, in order to
force all clients to pay much more in return for much longer confirmation times. All in name of freedom, of course...
