Kahit hindi ko nakikita ang inyong mga mukha, Manigong/Masaganang Bagong Taon sa inyong lahat, italkers...   At maraming salamat sa inyong pagtulong sa pag-aaral ko ng Tagalog.  Magkita-kita tayo muli sa 2015!

"Kahit hindi mo makita..." = Even if I don't see...

"Kahit hindi ko nakikita..." = Even if I am not able to/can't see...

“Manigo + ng” (prosperous) is an old word and I think I can safely say that it’s only used when we express this greeting.  “Masagana + ng” is another word for “prosperous” and you will sometimes hear the same greeting with the use of that word.

You do not really need a “saka” after “at” since you only meant “and”.  “At saka” would be “and also”.

“See you in 2015!” actually translates to “magkita tayo sa 2015!”, however, if we’d say it that way, we would most likely be telling that to just one person.  “Magkita-kita” would be applicable to a group, which is what you are actually addressing. Also, adding “muli” (again) would sound more natural in Tagalog.  Therefore, “magkita-kita tayo muli sa 2015!” would translate to “let’s all see each other again in 2015!”, which I think could be an interpretation of “see you in 2015!” just the same.

Masaganang Bagong Taon, Mrsjones!  :)

Manigong Bagong Taon!

Kahit hindi ko makita ang inyong mga mukhas, manigong Bagong Taon sa inyong lahat, italkers... at saka, maraming salamat sa tulong niyo para ng sa pag-aaral ko ng Tagalog. manood sa inyo Magkita tayo sa 2015!

the above is for the following sentence:
even though i can't see your faces, happy new year to all of you, italkers... and thank you very much for your assistance in my tagalog learning. see you in 2015!