For now, yes. No one can compete with BitcoinTalk when it comes to cryptocurrency forums (remember everything has an end). But as I've always said in this thread, competition sometimes benefits its users and community. Like what's happening now, before there was very little chance that you could also earn on AltcoinTalk. Look now that they're competing, your chance of earning on AltcoinTalk is higher compared before.
You have to understand that only earning opportunities can change the forum. Of course, it has a big effect. Even though altcoinstalks has a spike of visitors and users, maximum of them are originally from Bitcointalk. Do you think those users left BitcoinTalk? NO. I have teleported my account there and I write there as well. But, I am here as well.
If people join that forum and leave Bitcointalk, that would be a bad thing for this forum. But, this is not what happening now. I have seen their online counter and the number of daily visits. Unfortunately, it does not look real to me. I don't know the truth! I also agree that everything has an end.
I do not see other forums as a threat to Bitcointalk forum. Bitcointalk forum has made a name for itself over the years and more people are joining the forum without restrictions. One benefit members enjoy from building the forum is freedom. Freedom to post useful contents from any forum that are free from plagiarism. Bitcoin is not in any form of competition with other forums, infact the teleport feature makes it even more easier for Bitcointalk members to go in and out of other forums without losing their membership in the Bitcointalk forum. If other forums place restrictions on adverts and promotions from other forums, it is them dealing with their insecurities. Other forums are still trying to gather traffic on their platforms therefore, bringing contents from other platforms means diverting the attention of their forum members.