yes, it could be, but
i'd say '또 만나요' instead of '곧 만나요', and it can be used on line as well.
'곧 만나요' is just a statement, i don't think it is appropriate for spoken Korean.
'내일 거기서 만나요' also can be used on line depending on context.
like chat rooms on websites, but both expressions you mentioned can't be replaceable for the different meaning between them.
as for me, hardly use both of expressions.
when i say goodbye to finish chatting on line,
i usually say ' (그럼 다음에) 또 만나요(or 봐요)' which means 'see you around/later'.