  In order for neutralino dark matter to avoid being overproduced in the early
universe, these particles must annihilate (or coannihilate) rather efficiently.
Neutralinos with sufficiently large couplings to annihilate at such high a rate
(such as those resulting from gaugino-higgsino mixing, as in "well-tempered" or
"focus point" scenarios), however, have become increasingly disfavored by the
null results of XENON100 and other direct detection experiments. One of the few
remaining ways that neutralinos could potentially evade such constraints is if
they annihilate through a resonance, as can occur if 2$m_{\chi^0}$ falls within
about $\sim$10% of either $m_{A/H}$, $m_h$, or $m_Z$. If no signal is observed
from upcoming direct detection experiments, the degree to which such a
resonance must be tuned will increase significantly. In this paper, we quantify
the degree to which such a resonance must be tuned in order to evade current
and projected constraints from direct detection experiments. Assuming a future
rate of progress among direct detection experiments that is similar to that
obtained over the past decade, we project that within 7 years the light Higgs
and $Z$ pole regions will be entirely closed, while the remaining parameter
space near the $A/H$ resonance will require that $2m_{\chi^0}$ be matched to
the central value (near $m_A$) to within less than 4%. At this rate of
progress, it will be a little over a decade before multi-ton direct detection
experiments will be able to close the remaining, highly-tuned, regions of the
$A/H$ resonance parameter space.

High Energy Physics - Phenomenology;Cosmology and Nongalactic Astrophysics