The French were always at least one step behind the Prussians.
They had seen the impact of the needle rifles on the battlefields of 1866, and devoted their efforts to the manufacture of Chassepot rifles, which were better than the needle rifles. However, they did not consider the adoption of the infantry tactics developed by the Prussians in the second Danish war, and successfully implemented in the war against Austria, and relied on the doctrine of defense in strongpoints, to maximize the effect of rifle volleys with better effective range. In all honesty, the more flexible infantry tactics adopted by Prussians needed more time to be learnt by conscripts, and would have required a complete overhaul of the army.
There was no time nor money to develop, test and adopt better artillery (and develop the new tactics to employ them). Krupp in Germany had started developing new and more effective artillery pieces by the middle of 1850s, but even the Prussian army did not switch to them until after the war of 1866, and in 1870 the most of the field guns were older models.
I think the better artillery would help, but the incompetence of the French leadership meant that France would still lose the Franco-Prussian War. Maybe not so much of a 1-sided slaughter, but France would still have lost.