I’m wondering if Jetpack Security will ever proactively protect against attacks like Wordfence or Sucuri.

Scanning and brute force protection are good but it it’s hard to justify Jetpack Security’s cost without some type of firewall. You get more protection at a lower price with a setup like WordFence Premium + UpdraftPlus Premium, especially at scale. Throw in automatic updates and hosting-level backups and Bob’s your uncle.