First, the news:
Okay, so the San Diego Chargers don't believe that a 2015 ballot measure can happen. That's fine. They're entitled to that opinion.
It doesn't mean that it won't happen or can't happen. In fact, Speaker of the Assembly Toni Atkins has already said she'd push through a CEQA exemption through the State Legislature if the city and the Chargers could reach a deal.
What are the Chargers really saying here?
To me, this is a "We're not going to talk with you anymore" statement without actually saying those words. The team will now delay or turn down meetings and say that they don't want to waste their time on something they don't believe will happen. This is an end to the negotiations.
From here, the Chargers seem to be totally focused on getting a deal done in Inglewood or Carson. Perhaps, if one of those doesn't happen for them, they will come back to the negotiating table with their tail between their legs. However, San Diego now needs Los Angeles to fail as an option because the Chargers will consider staying.
This is probably the worst day in Chargers history (so far). What a shame.