Reference for electronegativities of different metal oxidation states
Pearson conveniently lists cumulative experimental data in the 1988 paper [1], referrring to the earlier work of Moore [2].
Selected values of $I$ (ionization potential), $A$ (electron affinity), $χ$ (absolute electronegativity – probably, that's what you are looking for) and $η$ (absolute hardness) for iron and cobalt cations are:

Table I. Experimental Parameters for Monatomic Cations (eV)
$$
\begin{array}{lcccc}
\hline
\text{ion} &amp; I &amp; A &amp; χ &amp; η \\
\hline
\ce{Fe^2+} &amp; 30.65 &amp; 16.18 &amp; 23.42 &amp; 7.24 \\
\ce{Fe^3+} &amp; 54.8 &amp; 30.65 &amp; 42.73 &amp; 12.08 \\
\ce{Co^2+} &amp; 33.50 &amp; 17.06 &amp; 25.28 &amp; 8.22 \\
\ce{Co^3+} &amp; 51.3 &amp; 33.50 &amp; 42.4 &amp; 8.9 \\ 
\hline
\end{array}
$$

So it looks like the relation is a bit different:
$$\ce{Fe^2+} &lt; \ce{Co^2+} &lt; \ce{Co^3+} &lt; \ce{Fe^3+}$$
Complete table as a screenshot:



References

Pearson, R. G. Absolute Electronegativity and Hardness: Application to Inorganic Chemistry. Inorganic Chemistry 1988, 27 (4), 734–740. https://doi.org/10.1021/ic00277a030.
Moore, C. E. &quot;Ionization Potentials and Ionization Limits&quot;; Natl. Stand. Ref. Data Ser. (U.S. Natl. Bur. Stand.); 1970, NSRDS-NBS 34. (NIST - PDF)