Don't know. As you said, Jigglypuff last appeared in AG039 "A Pokéblock Party!", but after that it completely vanished. Being that AG039 took place in Hoenn which is an island region, it would seem like Jigglypuff is somehow travelling place to place (possibly by puffing up and floating), possibly trying to find someone who would listen to its song fully without falling asleep. Whether we may or may not encounter Jigglypuff again is unknown, as it would have to be a chance encounter if it is doing what I said it was. It is also very possible that the story writers could have simply shoved Jigglypuff to the side, deciding that the Team Rocker running gags were more then enough comedy (which is the only thing Jigglypuff brought to the show).

I thought you said you knew everything about Pokemon?

You want a more direct answer? Fine, here is is: Don't hold your breath. Seems like the writers decided to drop the Jigglypuff running joke and it doesn't look like they'll be reviving it anytime soon, or ever.

It never did. Between its capture in EP019 "Tentacool & Tentacruel" and being left at the Cerulean Gym in EP061 "The Misty Mermaid", it rarely saw any screentime.

How can somebody know everything about Pokemon when even the creators don't know everything? How is Pikachu315111 supposed to know if Jigglypuff is supposed to come back, if Jigglypuff's last appearance was "A Pokeblock Party" period, dub, original. The most recent episode Jigglypuff was in "A Pokeblock Party." There's no secret episode Jigglypuff has been in since then, there's no conspiracy.

When Pikachu315111 says he doesn't know, no one knows. All he can give you is his best opinion on the matter.

Misty's Special Lure made an appearance in DP034 "Buizel Your Way out of This", but other then that Misty herself has no made an appearance. However Misty's Japanese Voice Actor, Mayumi Iizuka, stated Misty will be making an appearance in Sinnoh (but it is under debat right now whether she meant in person, or a reference to Misty which was presented with her Special Lure appearing in DP034).

No, at least not an official one.

Between EP052 "Princess vs. Princess" and EP146 "Tricks of the Trade", Lickitung wasn't used a lot, pretty much only when Team Rocket sends out all of their Pokemon to attack Ash and co. (though most of the time, Jessie uses just Arbok). It actually never appeared in Kanto besides for the episode it was captured in, but during the Orange Islands and Johto did it start appearing alongside all of Team Rocket's Pokemon:

Orange Islands: (Season 2)
EP086 "Pikachu Re-Volts"
EP088 "In the Pink"
EP094 "Snack Attack"
EP097 "Tracey Gets Bugged"
EP098 "A Way Off Day Off"
EP108 "Pokémon Double Trouble"
EP115 "A Tent Situation"

The Johto Journeys: (Season 3)
EP117 "Don't Touch That 'dile"
EP119 "A Sappy Ending"
EP128 "The Whistle Stop"
EP129 "Ignorance is Blissey"
EP130 "A Bout With Sprout"
EP140 "Wired for Battle!"
EP145 "A Farfetch'd Tale"

Micle Berry (#61) were held by Movie 11 promotional Shaymin.
Custop Berry (#62) were held by Movie 11 promotional Regigigas.
Jaboca Berry (#63) were held by Jirachi given out during the Tanabata festival in Japan at Toys "R" Us store and the Pokemon Center on Augest 18th through 31st.
Rewop Berry (#64) Have not officially been released.

I don't know. This falls under the catagory of the Pokemon Company's plans which only they know. You can ask Pokemon.com's Mailbag. To ask them your question, click HERE, and then click on where it says "Email Us Here!" under the top bar but above the Recent Mailbags to the right. A window should pop up with "mailbag@pokemon.com" in the "To". Type in a "Subject" and then ask them your question in the text box below.

As for Season 9, yes that is out on a Box Set. As for Season 10, no Season that features the Sinnoh region has been released in a Box Set as of yet.