Judging from the abstract to the paper and reports they have given at scientific conferences they are aguing in favor of large-scale water in the northern plains of Mars:

Spectral evidence for weathered basalt as an alternative to andesite in the northern lowlands of Mars.
"The coincidence between locations of such altered basalt and a suggested northern ocean basin implies that lowland plains material may be composed of basalts weathered under submarine conditions or weathered basaltic sediments transported into this depocentre."
Nature, May 16, 417, 263 - 266 (2002)
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v417/n6886/abs/417263a_fs.html

Andesite or Weathered Basalt? Martian Surface Compositions from MGS-TES.
Lunar and Planetary Science XXXIII (2002).
M. B. Wyatt and H. Y. McSween, Jr., Dept. of Geological Sciences and Planetary Geosciences Institute, University of Tennessee, Knoxville, TN, 37996-1410 (mwyatt1@utk.edu).
"Alternative Hypothesis. The northern lowlands lie, for the most part, below the 0-km elevation datum, and lakes or oceans, possibly fed by large outflow channels originating in the southern highlands, may have occupied this region. We examine if these surface materials may be reclassified as basalts altered in a low-temperature submarine environment."
http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1702.pdf

AN ALTERNATIVE HYPOTHESIS FOR BASALT AND ANDESITE ON MARS: GLOBAL SURFACE COMPOSITIONS FROM MGS-TES.
64th Annual Meteoritical Society Meeting (2001).
M. B. Wyatt and H. Y. McSween, Jr., University of Tennessee, Knoxville,
TN 37996-1410 (mwyatt1@utk.edu).
"We examine an alternative hypothesis that the martian surface is entirely dominated by basaltic lavas and that Type 2 surface materials are basalts weathered in a submarine environment."
http://www.lpi.usra.edu/meetings/metsoc2001/pdf/5392.pdf

I would say that most Mars scientists would guess that Mars Odyssey will provide further evidence for water on Mars rather than less.

Bob Clark