I do not want this thread to be derailed by a discussion on how likely it is that the game is dying soon, but let us assume for a moment that this was the case and the designers would ask you to submit him a list with 5 (types of) heroes you would like to have in the last packs. You could choose on whatever criteria you like (which tribe needs some more support, which are you favorites, etc.).
As you will see from my list, I am an elf guy and as I am not an expert on Tolkien lore I will not chose a particular character for the most part (and you also do not need to do that.
1. Silvan Spirit Hero: medium threat level with either a defensive or willpower focus. Galadriel is obviously very strong (and technically Noldor) and Legolas does not really fit the Silvan theme. So I really feel that this is the sphere where another sylvan hero would be the most welcome
2. Silvan Tactics Hero: medium to high threat and hopefully one of the better defenders in the game (in that case the Spirit hero should be willpower focused). Tactics Legolas is to this day a very good hero, but it would be great to have the option to be able to mix it up a bit. Especially considering that Tactics has quite a few really good silvan cards.
3. Noldor tactics (preferably Glorfindel): as with silvan, Noldor only has one tactics option and Elladan comes with the burden that you cannot really play him without Elrohil. Therefore enter Glorfindel. Yes, we do already have two versions, but Lore Glorfindel has one of the weakest abilities of any hero and Spirit Glorfindel while being very good only has a negative ability and is not terribly exciting to play. Give us a Glorfindel with a 12 threat and a powerful and especially interesting ability that is worth every point. Make him one of the stand-out heroes in the game. He should be the focal point of decks and not a pure stats guy (as spirit Glorfindel basically is).
4. Noldor Leadership (preferably Elrond): Yes, we will get Gildor, but I am not really excited for him. Lore Elrond is probably perfect, so my feelings about the Leadership Noldor being Elrond are not as strong as with Glorfindel in tactics (a Glorfindel leadership hero would obviously also be an option).
5. Spirit Aragorn: To complete the collection and it would just feel right to close the game with the character that was printed on the first card of the core set. His ability should make him a strong defender as we have had an readying Aragorn, a threat level-controlling-Aragorn, an (kind of) attack-boosting Aragorn.
Honorably mentioned: A Rohan Lore Hero and an Hobbit Leadership Hero.
If you like you could also name one player card that you would hope for. Mine would be a Silvan weapon in Lore (granting +1 attack default and +2 if a special condition is met).
I am really looking forward to your ideas.