Business is business. Where the demand (and more importantly, profit) is, that's where they'd go. Even without the perception/accusation of their OLD scandal still hounding them in their home soil, it's likely T-ara (and even other groups/artists) would still expand, due to the heavily saturated Korean market (look at the ever growing number of girl groups alone). I say 'good' thing about the scandal is that they don't 'need' be tied down and not lose their initial/local fanbase. Talk about turning misfortune into (lucrative, hopefully) opportunities.
As the saying goes, strike while the iron is hot. If there is demand, it would be illogical to turn it down, unless a better option present itself (or that demand is detrimental in some way). Like their recent singles/albums have less than stellar sales, would it be a wonder if they tried/moved on their hand in other (and bigger) markets, especially if they are being invited?
Another thing, less domestic projects mean T-ara need not go 300% activities in at least 3 countries. They are reputed as one of the most overworked (at which they even have a clip complaining/demanding of having no breaks since debut) I shudder what state they would be in if they are moving all around in East Asia (and other parts of the world) all the time.
I acknowledge that having a strong and loyal fanbase is important as the core, as overseas activities may only be trendy in those countries (i.e. short term), but complaining about the lack of local activities is laughable in the least.
PS: I just hope the girls further improve their language skills (whether Japanese, Korean, English, etc). Any work that requires regular interaction with foreigners (relatively to oneself), good communication skills are a must, especially in an industry T-ara is in.