The Baal Shem Tov, or Besht — the founder of Chasidism —
met the soul of the Messiah during an ascent to heaven.
The Besht asked him, "When will the Master come?"
The Messiah answered, "When your wellsprings break forth to the outside!"
(from a letter written by the Besht to his brother-in-law about one of his soul ascents)
Should we still observe Tish'a B'Av now that we "have" Israel?
It's not necessary to ask this question inside Orthodoxy, because people assume they should observe Tisha B'Av. But it is necessary in the other branches of Judaism, and it may still be important to ask the question within Orthodoxy, because observing the fast day without deepening its significance for this world and this time is also not enough.
Tish'a B'Av is not about mourning, though there is much to mourn, but about becoming refugees. Tish'a B'Av is not primarily about the end of sacrifices or the Temple – Chaza"l, the rabbis, figured out how to live without the Temple long ago. Rather, it's about homelessness, being thrown into a hostile world without shelter or protection, fleeing from war into famine—all things that are far too present in this world.
It's not even about sin, though Lamentations struggles with that idea. It's about living in a world where military force and political power are used to destroy both the guilty and the innocent, without distinction. It's also about confronting the ways in which we as individuals (and as a people) use our power and make others into refugees. On Tish'a B'Av, in a time when humanity is compromising the place we have on this planet, we need to ask ourselves: How do we treat homeless people? How do we treat refugees, immigrants, strangers? How can we leave enough space for all the other species on this earth? How can we respect this world as our home, so that we don't deprive the other species of their home?
The customs of Tish'a B'Av reflect some of these nuances: fasting is not only a mourning custom (as we know from Yom Kippur), it's also a way to experience living in a world where there's famine. This goes along with the fact that Tish'a B'Av is the only day there's permission to do things which cause oneself pain and discomfort (e.g. by sleeping on the floor or putting rocks in one's shoes). It's about experiencing the world as a refugee, as someone who has no food or bed, no place to wash, no change of clothes.
Israel gives us a chance to look at these bigger issues instead of having to worry only about our own survival. The existence of Israel is hardly a reason to take Tish'a B'Av less seriously, though it may give us new issues to ponder from the perspective of having power. For example, we need to ask ourselves about people who are becoming refugees inside Israel, e.g.: How should Israel treat the Bedouin living in "unrecognized villages"? What's happening to foreign workers, the poor, Ethiopian Jews? How can we protect African asylum-seekers, who are being called "infiltators" by the right-wing government and deported at the risk of their lives? When will Israel respect human rights and Palestinian lives in the Territories, even if it is also protecting its citizens?
Until we live in a world where there are no refugees, and where Israel is truly at peace with her neighbors, we need Tish'a B'Av.