Greek referandum will not affect anything at all. But in my opinion whatever the result will be, the pressure on $EURUSD will also increase. Hold on to your hats!
You saw what was the reaction on Monday. After Tsipras announced the referendum, there was heavy knee-jerk selling in illiquid Asian hours, then all they long buyers pushed it back above 1,1200.
The thing is, that you can never really know what a reaction might be... sometimes a bad news is good news. My opinion that a Grexit would be really supportive for EUR in general. Why on the other had if they stay in the Eurozone, that will also cause buying in EURUSD, as mkt would calm down, pricing out bearish EUR views + yesterday US NFP and unemployment was disappointing, and there is increasing chance FED will postpone its first rate hike to January/2016.
However as a technical trader we have to avoid thinking in "macro" or fundamental style. The only thing you can follow is Price action, and that is simply dull right now. EURUSD is still trading in a range. A break below 1,10 would be bearish, a break above 1,1350 would be very bullish. In between it is random, not trending.