So sharding is essentially centralizing a part of the decentralized network?
The nodes around a particular shard will then be more vulnerable, wont they? It is impossible for me to hit up the entire ETH network, but couldnt this present a single point of entry for hackers? Also, wouldnt we see an increased possibility of any applications tied to this shard having the ability to create more damage if there are security flaws in it?
Finally, will this really enable them to scale up?
It's not really centralising it, more so decreasing the security of a decentralised network.
As I mentioned in the post, a shard take over is possible, which answers your second question - and yes/no, because while shards are more susceptible to attacks, if they can't actually interact with other shards (instead use receipt tracking), then threats will be easily isolated, so it's a win-lose situation unfortunately. They're working on fixing this.
Yes, test net results have increased TPS by 233% already, with the aim of going even higher, although I don't know the exact number of TPS sharding will allow.
Thanks for the comment!