Well, I looked it up on the internet and it says that a Novelty Act is something which the audience would find amusing at first but soon its novelty wears off.
Hmmm...let's see. Weird Al has been releasing parodies since about 1983.
His most recent album (Mandatory Fun), released in 2014 was ranked #1 in the US, #3 in Canada, and #9 in Australia.
So, after about 30 years, he's lost so much popularity that his new album only made it into the top 10 in 3 countries.
Now let's consider the acts he parodied.
I Lost on Jeopardy was a parody of a Greg Kihn song. Greg Kihn's first album to make it into the Billboard 200 was Next of Kihn, in 1978. The most recent, was Citizen Kihn in 1985, so they had a run of almost 7 years.
Gump was a parody of Lump by The Presidents of the United States of America. They released two ranked albums, in 1995 and 1996, plus a compilation album that was ranked #198 in the UK in 1998.
Ricky was a parody of Toni Basil's "Micky". Toni Basil released albums in 1983 and 1984. The latter didn't chart as an album, but did contain one single that made it into the US Dance music chart.
Lest this get boring, I'll just list some more:
- King of Suede (Kind of Pain, the Police)
- Like a Surgeon (Like a Virgin, Madonna)
- Fat (Bad, Michael Jackson)
- Smells Like Nirvana (Smells Like Teen Spirit, Nirvana)
- I think I'm a Clone Now (I Think We're Alone Now, Tiffany)
- Achy Breaky Song (Achy Breaky Heart, Billy Ray Cyrus)
- Amish Paradise (Gangsta's Paradise, Coolio)
- It's all About the Pentiums (All About the Benjamins, Puff Daddy)
- Pretty Fly For a Rabbi (Pretty Fly for a White Guy, The Offspring)
- White and Nerdy (Ridin', Chamillionaire and Krayzie Bone)
- Canadian Idiot (American Idiot, Green Day)
- Perform This Way (Born This Way, Lady Gaga)
Green Day just released a new album this year. I can see Lady Gaga releasing more albums. Madonna might also. These will be noticeable to at least some degree. Greg Kihn (for one example) still seems to be cranking out new albums every few years, so I guess it wouldn't be a big surprise if he released at least a few more. Not likely to get a lot of interest though.
There will probably be at least a few more releases of material done by Nirvana, Queen, and Michael Jackson at some point or other. Not new material (obviously) but new releases of old material.
Weird Al is certainly a novelty act by most definitions. He's continued to release new material for far longer than most of the acts he parodied. In fact, at least out of those listed above, the only one I can see who really competes with him for longevity is Madonna (and potentially those that are still active, like Green Day and Lady Gaga). Quite a few of them had at most an album or two that sold reasonably well, but the number releasing reasonably successful albums in 3 or 4 different decades...is pretty small, to say the least.
So to answer the question directly, I'm going to say: "No, not necessarily".