Well, Hashem intended for Mankind to be vegetarians – it was only after the Mabul that He allowed the eating of meat, but ALWAYS with some restrictions (no eiver min hachai). When Bnei Yisroel ate meat, the restrictions went even further.
If we were vegetarian, however, and when the Beis Hamikdash is rebuilt Bimheira b’yameinu, how will vegetarians fulfill the mitzvah of certain types of korbonos, especially korbon Pesach?
All things should be in moderation, including the eating of meat.