Well Andreas Antonopoulos likes to put it differently and I personally believe he is most likely right. He says that we can be sure that Bitcoin gets attacked all the time. Maybe not so much anymore these days but the reason that we believe it hasn't been attacked is that Bitcoin hasn't been successfully attacked yet. In Blockchain you either crack or it or you don't, it is a binary thing. If someone breaks into your house it might be different as you may be able to see some evidence afterwards even though the attack wasn't successful.
Exactly, Bitcoin gets attacked all the time, probably not so much as before! It's crazy to think that hackers, big corporations, and even governments didn't try to do something with Bitcoin... with all their man and computer power, crazy big funds! And Bitcoin is still here and alive! Now probably there are some enthusiasts who are still trying to hack Blockchain, but it's very difficult for them to do that... Theoretically, anything is possible if you are imaginative, but I really doubt that something will happen to Bitcoin in the near future!