It appears that in December 1863, Col Slemons is still in Mississippi, but many of his unit have deserted and gone home to Arkansas.

HEADQUARTERS FIFTH MILITARY DISTRICT,
DEPARTMENT OF MISSISSIPPI AND EAST LOUISIANA,
Grenada, August 24, 1863.
Major General S. D. LEE,
Commanding Cavalry:

GENERAL: In compliance with your request I have the honor to submit the following report showing the disposition of the forces under my command at the time of the recent raid by the enemy:
...I learn from Colonel Slemons, Second Arkansas Regiment, who was in command during my absence, that when he reached Grenada on his retreat from Panola he had but little more than 700 men with him. This was composed of the Second Missouri and Seventh Tennessee Regiments and Willis' (Texas) battalion, the Second Arkansas Regiment, reduced by desertion to 42 men,....
I am, general, very respectfully, your obedient servant,
JAS. R. CHALMERS,
Brigadier-General.
http://ehistory.osu.edu/books/official-records/053/0543

HEADQUARTERS CAVALRY IN MISSISSIPPI,
Morton, September 1, 1863.
[Colonel B. S. EWELL,
Assistant Adjutant-General:]
SIR: As the result of my recent tour of inspection I have the honor to submit the following report:....
Chalmers' cavalry command on Tallahatchie, extending as far east as Rocky Ford, consists of First [Seventh] Tennessee, Second Missouri, Willis' (Texas) battalion, and Second Arkansas, numbering, all told, not to exceed 600 effective men, the regiments being much reduced; one, the Second Arkansas, having but 40 enlisted men.
http://ehistory.osu.edu/books/official-records/053/0576

HEADQUARTERS CAVALRY IN MISSISSIPPI,
Canton, September 16, 1863.
Brigadier General J. R. CHALMERS,
Commanding Cavalry Brigade, Grenada, Miss.:
....Your request to have Colonel Slemons ordered to Arkansas is approved by the major-general commanding, and you will issue the order accordingly.
S. COOPER,
Adjutant and Inspector General.
http://ehistory.osu.edu/books/official-records/053/0654

SPECIAL ORDERS,
HDQRS. FORREST'S CAVALRY DEPT.,
Numbers 14.
Near Como, Miss., January 25, 1 864.

I. Colonel W. F. Slemons, Second Arkansas Cavalry, is relieved from duty with this command, and will turn over his brigade to the senior officer present and report to Major General N. B. Forrest for orders. In parting with Colonel Slemons, the brigadier-general commanding feels that he has lost a bold and gallant officer, whose long service in the cavalry of this department has won for him the respect and confidence of his commanding officers and the love and obedience of his troops. The officers of his staff will remain on duty until relieved.
* * * * * *
By order of Brigadier-General Chalmers:
A. G. MILLS,
Acting Assistant Adjutant-General.
http://ehistory.osu.edu/books/official-records/058/0614